The long term goal of this investigation is to understand the role of the mitochondrial outer membrane in cellular phospholipid synthesis. In this project, we will focus our attention on mitochondrial glycerophosphate acyltransferase which we have recently purified to homogeneity, and also on another protein -- the microsomal glycerophosphate acyltransferase which we now propose to purify. The purification will be attempted by successive chromatography on Sepharose Q Fast Flow, Bio-Gel HT and glycerol 3-phosphate-agarose affinity column. We will biochemically characterize the purified proteins, examine how different phospholipids modulate their activities, and will determine the amino acid sequence of the purified acyltransferases by sequencing the corresponding cDNA molecules. We will examine if Ehrlich ascites tumor cells, which show a random distribution of fatty acids in the sn1 and sn2 positions of some of their phospholipids and has no detectable mitochondrial glycerophosphate acyltransferase, actually contain the enzyme protein. These cells either do not contain the mitochondrial acyltransferase or, they have the enzyme protein which remains inhibited by the membrane phospholipids. We will attempt to demonstrate in vivo that mitochondrially made lysophosphatidic acid can be transported to the endoplasmic reticulum for being converted to phosphatidic acid and if fatty acid binding protein is involved in this intracellular transport of lysophosphatidic acid. We will examine if the well known modulators of energy-linked metabolic pathways and phosphorylation-dephosphorylation mechanism also regulate the mitochondrial and microsomal glycerophosphate acyltransferase. This investigation is important in molecular cell biology because it will lead to the understanding of (i) the structure and function of mitochondriaI and microsomal glycerophosphate acyltransferase which catalyze the committed step in glycerophospholipid biosynthesis, (ii) the regulation of the asymmetric distribution of fatty acids in cell glycerophospholipids and (iii) the contribution of the mitochondrial outer membrane in cellular phospholipid metabolism.